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Two-Phase Spray Cooling with Water/2-Propanol Binary Mixtures for High Heat Flux Focal Source (open access)

Two-Phase Spray Cooling with Water/2-Propanol Binary Mixtures for High Heat Flux Focal Source

Two-phase spray cooling has been an emerging thermal management technique offering high heat transfer coefficients and critical heat flux levels, near-uniform surface temperatures, and efficient coolant usage that enables to design of compact and lightweight systems. Due to these capabilities, spray cooling is a promising approach for high heat flux applications in computing, power electronics, and optics. Two-phase spray cooling inherently depends on saturation temperature-pressure relationships of the working fluid to take advantage of high heat transfer rates associated with liquid-vapor phase change. When a certain application requires strict temperature and/or pressure conditions, thermo-physical properties of the working fluid play a critical role in attaining proper efficiency, reliability, or packaging structure. However, some of the commonly used single-component working fluids have relatively poor properties and heat transfer performance. For example, water is the best coolant in terms of properties, yet in certain applications where the system operates at low temperature ambient, it cannot be implemented due to freezing risk. The common solution for this problem is to use the antifreeze mixtures (binary mixtures of water and alcohol) to reduce the freezing point. In such cases, utilizing binary mixtures to tune working fluid properties becomes an alternative approach. This study has …
Date: December 2016
Creator: Obuladinne, Sai Sujith
System: The UNT Digital Library
African American Children in the Jim Crow North:  Learning Race and Developing a Racial Identity (open access)

African American Children in the Jim Crow North: Learning Race and Developing a Racial Identity

This thesis explores how African American children in the North learned race and racial identity during the Jim Crow era. Influences such as literature, media, parental instruction, interactions with others, and observations are examined.
Date: December 2016
Creator: Beal, Michele
System: The UNT Digital Library
Exploratory User Research for a Website that Provides Resources for Educators of American Indian Students in Higher Education (open access)

Exploratory User Research for a Website that Provides Resources for Educators of American Indian Students in Higher Education

Several studies have indicated that American Indian students in the United States higher education system confront unique challenges that derive from a legacy of colonialism and assimilationist policies (Huff 1997). Several scholars, American Indian and non-Native alike, have explored the effects of this history upon students in higher education (Brayboy 2004; Guillory and Wolverton 2008; Waterman and Lindley 2013). Very few, however, have explored the role of the educators of American Indian students, and most of the literature focuses on K-12 educational settings (McCarty and Lee 2014; Yong and Hoffman 2014). This thesis examines exploratory user research conducted to generate a foundational understanding of educators of American Indian students in higher education. Utilizing methods from design anthropology and user experience, semi-structured interviews and think-aloud sessions were conducted, almost exclusively virtually, for 17 participants. This research was conducted for a client, Fire & Associates, as part of the applied thesis process. Findings revealed a complex web of needs for educators of American Indian students in higher education related to teaching diverse students, the use of media and technology in the classroom, and the process of networking among other educators. The research culminated in content and design implications for the Fire & …
Date: December 2016
Creator: Roth, Heather S.
System: The UNT Digital Library
Using Relational Responding to Examine the Acquisition of Mindfulness and Meditation Material: An Analogue Study (open access)

Using Relational Responding to Examine the Acquisition of Mindfulness and Meditation Material: An Analogue Study

Mindfulness meditation is a growing area of interest for both mental health professionals and the general public alike. Beneficial outcomes are associated with these practices, although the variety of measurement techniques makes research difficult to interpret. Definitions of these constructs are varied, and anecdotal accounts point to the idea that many people hold misconceptions about mindfulness and meditation, even when meanings are made clear. Still, no formal research has been published on misconceptions of mindfulness – or, if they exist, how such misinformation affects acquisition of related skills. Furthermore, mindfulness has been incorporated into therapeutic modalities without much consideration for context, including the client's learning history. The current analogue study examined how the presentation of mindfulness meditations (i.e., inaccurate rationale/meditation and accurate rationale/meditation) affects an individual's practice. Specifically, self-reported mindfulness and meditation skills, mood questionnaires, a matching-to-sample task, and qualitative measurements were used to assess acquisition. Although primary hypotheses did not yield significant findings, results from both preliminary and exploratory analyses demonstrate significant findings with regard to teaching, learning, and measurement related to mindfulness meditation. The results, future directions, and limitations are discussed.
Date: December 2016
Creator: Lester, Ethan G.
System: The UNT Digital Library
What's in Your Garden? Assessing the "Eco-friendliness" of Plant Choices of Denton, Texas Gardeners (open access)

What's in Your Garden? Assessing the "Eco-friendliness" of Plant Choices of Denton, Texas Gardeners

Urbanization is seen as a threat to biodiversity within urban ecosystems, which are largely reliant on humans for their composition. Two types of extremes exist in the spectrum of urban domestic gardens; on one end, the typical urban garden which is planted by landscapers at the time the house is built and is generally left unchanged, and, at the other, a "wild" landscape planted entirely with native plants which provides habitat for native fauna and pollinators. This study assesses the plant choices made by members of organized gardening groups-the Denton County Master Gardeners (DCMG), the Elm Fork Master Naturalists (EFMN), the Trinity Forks Native Plant Society (TFNPS), and Keep Denton Beautiful (KDB)-and toward which extreme these choices put these gardens on the psectrum. TFNPS and EFMN both fall closer to the wild garden extreme, with TFNPS the closest to a "wild garden." DCMG was almost directly between the two extremes, but fell closer to the typical urban garden. By looking at how these groups manage their gardens, we begin to understand the ways in which gardeners can mitigate and soften the harsh changes between wild landscapes and urban environments. Collaboration between groups could have the potential to encourage more people …
Date: December 2016
Creator: Cloutier, Andrea Nicole
System: The UNT Digital Library
The Relation of Perceived Motivational Climate, Mindset, and Achievement Goal Orientation to Grit in Male High School Soccer Players (open access)

The Relation of Perceived Motivational Climate, Mindset, and Achievement Goal Orientation to Grit in Male High School Soccer Players

Grit is defined as "perseverance and passion for long-term goals." Although studied in relation to various outcomes, such as retention and academic performance, few studies have examined variables that may contribute to grit's development. Further, few studies have examined this construct in relation to sport performance or within athletic environments, despite its clear connection to sport-related constructs like mental toughness and resilience. Thus, based in achievement motivation theory, this study examined the relations of the perceived motivational climate as defined by athletes' perceptions of the coaches' behaviors (task vs. ego), athletes' perceptions of their achievement goal orientation (task vs. ego), athletes' perceptions of their implicit theory (i.e., fundamental beliefs regarding whether or not ability can change; growth vs. fixed), and athletes' perception of their level of grit. Male varsity soccer players (N = 81; Mage = 15.80 ± .81) from a large metropolitan area in the south central U.S. completed questionnaires measuring these achievement motivation constructs. The full regression model was significant, accounting for 18% of the grit variance, F(6, 74) = 2.77, p = .017. Within the full model, having a growth mindset (β = .25, p = .035) and endorsing a task goal orientation (β = .36, p …
Date: December 2016
Creator: Albert, Erin D.
System: The UNT Digital Library
Analyzing Tuberculosis Vulnerability and Variables in Tarrant County (open access)

Analyzing Tuberculosis Vulnerability and Variables in Tarrant County

Over 9 million new cases of tuberculosis (TB) were reported worldwide in 2013. While the TB rate is much lower in the US, its uneven distribution and associated explanatory variables require interrogation in order to determine effective strategies for intervention and control. However, paucity of case data at fine geographic scales precludes such research. This research, using zip code level data from 837 confirmed TB cases in Tarrant County obtained from Texas Department of State Health Services, explores and attempts to explain the spatial patterns of TB and related risk markers within a framework of place vulnerability. Readily available census data is then used to characterize the spatial variations in TB risk. The resulting model will enable estimations of the geographic differences in TB case variables using this readily available census data instead of time-consuming and expensive individual data collection.
Date: December 2016
Creator: McGlone, John Francis
System: The UNT Digital Library
The Creation of Fictional History in the Tequila Industry (open access)

The Creation of Fictional History in the Tequila Industry

The creation of fictional history in the tequila industry due to changes in government policy, trade agreements and big business.
Date: December 2016
Creator: Nichols, Cynthia A.
System: The UNT Digital Library
Improving the Long-term Performance of PVC Compositions (open access)

Improving the Long-term Performance of PVC Compositions

PVC are extensively applied in many fields, such as cables, pipes, vehicles, shoes, toys and infusion bags. Generally, plasticizers are blended with PVC to improve the ability of process in industrial production; however, the toxic plasticizers will gradually migrate to the surface of products and such a leakage results in brittleness of plasticized PVC and environmental pollution. In other words, humans are frequently exposed to the potential risks. According to previous researches, cross-linked PVC was proved that it was able to hinder the migration of plasticizer. Thus, in this research, we selected some commercially used cross-linking agents and employed six different tests based on mechanical, tribological and microscopy analysis in order to seek the best solution against plasticizer migration. Thus, we expected to develop a cross-linked flexible PVC which performed improved long-term performance and extended lifetime.
Date: December 2016
Creator: Yang, Yu Chia
System: The UNT Digital Library
Negotiated Living: An Ethno-Historical Perspective of Punta Allen (open access)

Negotiated Living: An Ethno-Historical Perspective of Punta Allen

Situated within the jurisdiction of the Municipality of Tulum and within the Sian Ka'an Biosphere gives the village of Punta Allen a distinctive agency in determining their role in the on-going development of tourism in the region that is not given to other communities in the state. This unique circumstance facilitates a dialogue between the reserve, the municipality, and the business cooperatives of Punta Allen that produce a negotiated living. Through the negotiations with the reserve and Tulum, the lobster fishing and tourism cooperatives are given the opportunity to have a relatively significant role in determining the future of Punta Allen in regards to tourism.
Date: December 2016
Creator: McRae, David Thomas
System: The UNT Digital Library
An Evaluation of Correspondence between Preference and Performance under a Progressive Ration Schedule with College Students (open access)

An Evaluation of Correspondence between Preference and Performance under a Progressive Ration Schedule with College Students

Preference assessments are used in clinical settings to identify stimuli with reinforcing potential. The progressive-ratio schedule has shown to be useful in clinical assessments in identifying stimuli with stronger reinforcer efficacy that corresponds to formalized assessments.The current study utilized a progressive-ratio schedule to compare videos of high and low preference assessed by verbal reports of preference with college students. Results indicated breakpoints were higher for high preferred videos than low preferred videos for three out of five participants, but preference was not indicative of performance.
Date: December 2016
Creator: Johnson, Jamarious
System: The UNT Digital Library
Ethiopian Coffee Stories: Applied Research with Sidama Coffee Farmers Combining Visual and Ethnographic Methods (open access)

Ethiopian Coffee Stories: Applied Research with Sidama Coffee Farmers Combining Visual and Ethnographic Methods

The purpose of this study is to demonstrate the value of visual research methods to applied anthropology in the context of exploratory research with farmers in Ethiopia. The three methods of photo-elicitation, participatory photography, and ethnographic film, enrich and expand ethnographic methods to support the client's objective of supporting farmers. The applied project constructs a narrative from the local perspective to help consumers learn more about farmers' lives. The research focuses on specific farmers, and their experiences with direct fair trade and coffee farming. The client sees the application of research produced by ethnographic and visual methods as a good direction not only for his company, but the Fair Trade Industry as a whole.
Date: December 2016
Creator: Suter, Paula J.
System: The UNT Digital Library
Dissimilar Friction Stir Welding Between Magnesium and Aluminum Alloys (open access)

Dissimilar Friction Stir Welding Between Magnesium and Aluminum Alloys

Joining two dissimilar metals, specifically Mg and Al alloys, using conventional welding techniques is extraordinarily challenging. Even when these alloys are able to be joined, the weld is littered with defects such as cracks, cavities, and wormholes. The focus of this project was to use friction stir welding to create a defect-free joint between Al 2139 and Mg WE43. The stir tool used in this project, made of H13 tool steel, is of fixed design. The design included an 11 mm scrolled and concave shoulder in addition to a 6 mm length pin comprised of two tapering, threaded re-entrant flutes that promoted and amplified material flow. Upon completion of this project an improved experimental setup process was created as well as successful welds between the two alloys. These successful joints, albeit containing defects, lead to the conclusion that the tool used in project was ill fit to join the Al and Mg alloy plates. This was primarily due to its conical shaped pin instead of the more traditional cylindrical shaped pins. As a result of this aggressive pin design, there was a lack of heat generation towards the bottom of the pin even at higher (800-1000 rpm) rotation speeds. This …
Date: December 2016
Creator: Reese, Gregory A
System: The UNT Digital Library
Sliding Friction and Wear Behavior of High Entropy Alloys at Room and Elevated Temperatures (open access)

Sliding Friction and Wear Behavior of High Entropy Alloys at Room and Elevated Temperatures

Structure-tribological property relations have been studied for five high entropy alloys (HEAs). Microhardness, room and elevated (100°C and 300°C) temperature sliding friction coefficients and wear rates were determined for five HEAs: Co0.5 Cr Cu0.5 Fe Ni1.5 Al Ti0.4; Co Cr Fe Ni Al0.25 Ti0.75; Ti V Nb Cr Al; Al0.3CoCrFeNi; and Al0.3CuCrFeNi2. Wear surfaces were characterized with scanning electron microscopy and micro-Raman spectroscopy to determine the wear mechanisms and tribochemical phases, respectively. It was determined that the two HEAs Co0.5 Cr Cu0.5 Fe Ni1.5 Al Ti0.4 and Ti V Nb Cr Al exhibit an excellent balance of high hardness, low friction coefficients and wear rates compared to 440C stainless steel, a currently used bearing steel. This was attributed to their more ductile body centered cubic (BCC) solid solution phase along with the formation of tribochemical Cr oxide and Nb oxide phases, respectively, in the wear surfaces. This study provides guidelines for fabricating novel, low-friction, and wear-resistant HEAs for potential use at room and elevated temperatures, which will help reduce energy and material losses in friction and wear applications.
Date: December 2016
Creator: Kadhim, Dheyaa
System: The UNT Digital Library
Cyclic Polarization of AA 3102 in Corrosive Electrolytes Containing Sodium Chloride and Ammonium Sulfate (open access)

Cyclic Polarization of AA 3102 in Corrosive Electrolytes Containing Sodium Chloride and Ammonium Sulfate

Corrosion of all aluminum microchannel heat exchangers present a challenge in automotive and heating, ventilation, and air conditioning (HVAC) industries. Reproducibility of Salt Water Acetic Acid Test (SWAAT) has been questioned and a need to new corrosion tests with better reproducibility has risen. Cyclic polarization, that is an electrochemical test, was explored for its suitability for the assessment of AA 3102 tube material that is currently a popular aluminum alloy used in manufacturing of heat exchanger. Corrosive electrolytes containing 3.5 % sodium chloride with 0.5 % ammonium sulfate (high chloride) or 0.5 % sodium chloride with 3.5 % ammonium sulfate (high sulfate) at their pH or acidic (pH=4) were used to measure corrosion potential (Ecorr), protection potential (Epp), pitting potential (Epit), Tafel constants (βa and βc), corrosion rate (mpy). Corrosive electrolyte used in SWAAT test (4.2% Sea Salt at pH 2.9) was also used to compare corrosion resistance of AA 3102 in SWAAT electrolyte compared to the other electrolytes used in this research. Scanning electron microscopy (SEM) was used to observe and document sample surface corrosion damage after each electrochemical test on all samples. Results of the cyclic polarization tests indicated that SWAAT electrolytes was the most aggressive electrolyte resulting …
Date: December 2016
Creator: Dorreyatim, Mohammad
System: The UNT Digital Library
Exploring Ahope Client Satisfaction and Attitudes (open access)

Exploring Ahope Client Satisfaction and Attitudes

I led a participatory action research (PAR) project with the staff and homeless clients of Ahope Day Center in Asheville, North Carolina, which was meant to evaluate client satisfaction with services and attitudes about certain issues. Project is led by an inquiry group consisting of members of Ahope staff and Ahope clients. The project is a co-designed, co-implemented, and co-interpreted mixed-method evaluation of Ahope's services, client attitudes about education and the environment, client adaptive strategies, optimism levels, and a mapping of client daily routines. The data was collected through participant observation, document analysis, surveys, a listing activity, and informal interviews. Documents were coded using grounded theory and themes emerged related to the value of the intangibles of security, community, and ‘being seen' at Ahope while some suggestions were also made. Findings included client attitudes indicating the importance of the environment and education to clients, high optimism levels among clients, and a number of suggestions for the improvement of Ahope's services.
Date: December 2016
Creator: Johnston, Josiah Ramsay
System: The UNT Digital Library
Cognitive Engagement in Later Life: Descriptive and Explanatory Findings (open access)

Cognitive Engagement in Later Life: Descriptive and Explanatory Findings

Findings on the relationship between engagement in lifestyle and cognitive functioning are not consistent; some authors report that engagement in lifestyle predicts an individual's cognitive functioning; while other report that an individual's cognitive functioning predicts the type and level of engagement an individual participates in. The current study will use longitudinal data (N = 235) to investigate the bidirectional relationship between engagement (engaged lifestyle activities) and cognition (crystallized & fluid intelligence). Despite inconsistent findings it is proposed that cognitive functioning may be better understood when examining how stimulation of activity, need for cognition, and openness to experience affect engagement in an active lifestyle. As such the current study will investigate if stimulation of activity, need for cognition, and openness to experience moderate the relationship between engaged lifestyles and cognitive functioning. The results, limitations and implications are discussed.
Date: December 2016
Creator: Abdullah, Bashir
System: The UNT Digital Library
Unclean Slates: Stories (open access)

Unclean Slates: Stories

Unclean Slates: Stories is a collection of seven short stories that comments on the nature of family ties, and how such ties help form a sense of identity. Each story focuses on a separate protagonist, all of whom strive for a new beginning or an escape from some aspect of their current lives. The short story cycle of this collection is held together not by place or characters, but ultimately by the theme of wishing for a new beginning: they share a desire to fix some dissatisfying element of their lives. Mostly from the point of view of blue-collar characters leading mundane middle-class lives, these stories provide commentary on what it means to run from the conditions that make up one's sense of identity. Most of the revelations formed throughout these stories lead to a sense of acceptance of these conditions, and an understanding that family and history make up part of human consciousness. While the specific locations presented in these stories are not necessarily the same, each story seeks to focus on a location that proves to be fundamental to the makeup of the protagonist. The cities and geographic locations themselves are not as important as the specifics: the …
Date: December 2016
Creator: Gollahon, Catherine
System: The UNT Digital Library
The 50,000 Watt Blowtorch of the Great Southwest: The History of WBAP (open access)

The 50,000 Watt Blowtorch of the Great Southwest: The History of WBAP

This paper looks at the history of WBAP while examining how programming has changed from 1922-2014 and how WBAPs audience helped shape programming at the station. This paper reveals four formatting changes throughout the stations history and provides in-depth statistical analysis of how WBAPs audience changed during the stations 90 plus years of existence.
Date: December 2016
Creator: Dixon, Chad M
System: The UNT Digital Library
Teaching Water Safety Skills to Children with Autism Using Behavioral Skills Training (open access)

Teaching Water Safety Skills to Children with Autism Using Behavioral Skills Training

Behavioral skills training (BST) and in situ training (IST) have been evaluated as methods to teach different safety skills to individuals with developmental disabilities. Research on BST has examined topics such as gun safety, abduction prevention, poison avoidance, and sexual abuse prevention. A large safety issue that is missing from the literature is drowning prevention and water safety skills. Drowning is one of the most prevalent issues facing facing children with Autism Spectrum Disorder (ASD), particularly those who elope from their homes or caregivers. The current study aimed the effectiveness of using BST+IST to teach three water safety skills to three children with ASD. The intial form of intervention was BST with total task presentation of the skill, using verbal instruction, modeling, rehearsal, and feedback. If this intervention did not result in an increase in performance, the skill was broken down into individual component presentation, in which each component of the skill was taught using the same procedures. Results from the current study showed that BST+IST was effective in teaching all skills to all participants.
Date: December 2016
Creator: Tucker, Marilyse
System: The UNT Digital Library
Modeling of Fracture Toughness of Magnesium Alloy WE43 Before and After Friction Stir Processing (open access)

Modeling of Fracture Toughness of Magnesium Alloy WE43 Before and After Friction Stir Processing

Magnesium alloys are a popular research topic for structural applications because they have a lower density than conventional structural materials, including steel, titanium, and aluminum; however, the reliability and safety of their mechanical properties must be further proven. An important mechanical property for this purpose is fracture toughness, which is the measure of the material's resistance to crack propagation. In this study, a model of an experiment to investigate the fracture toughness of a magnesium alloy WE43 before and after friction stir processing (FSP) is developed, and the results are compared to those produced by a digital image correlation (DIC) system during an experiment from another paper. The model results of the material before FSP matched well with the DIC results, but the model of the material after FSP only partially matches the DIC results. In addition, a theoretical approach to calculating the standard fracture toughness value, KIc, from the modeling results is proposed, and is found to be a conservative approach.
Date: December 2016
Creator: Lipscomb, Celena Andrea
System: The UNT Digital Library
Analysis of Students' Knowledge, Perceptions, and Interest in Engineering Post Teacher Participation in a National Science Foundation (NSF) Research Experience for Teachers (RET) Professional Development (open access)

Analysis of Students' Knowledge, Perceptions, and Interest in Engineering Post Teacher Participation in a National Science Foundation (NSF) Research Experience for Teachers (RET) Professional Development

This study examined the impact of the National Science Foundation's Research Experience for Teachers (RET) in engineering at University of North Texas on students after their teachers' participation in the program. Students were evaluated in terms of self-efficacy, knowledge of engineering, perceptions of engineering, and interest in engineering. A 22-item Likert pre/post survey was used for analysis, and participants included 589 students from six high schools, one middle school, and one magnet school. Paired surveys were analyzed to determine if there was a statistically significant difference in attitudes and knowledge after teachers implemented lessons from their time at the RET. Surveys were also analyzed to determine if there was a statistically significant difference in student response based on gender or student school type. Results showed no statistically significant difference in the self-efficacy of students, however there was a statistically significant difference in knowledge, perceptions, and interest in engineering. In addition, there was a statistically significant difference between genders on an isolated question, and seven out of the 22 Likert questions showed a statistically significant difference between student school types.
Date: December 2016
Creator: Reeder, Christina
System: The UNT Digital Library
When to correct errors when teaching a new task to children with autism (open access)

When to correct errors when teaching a new task to children with autism

The purpose of this experiment was to investigate Tosti's proposal about the timing of feedback. The study examined whether it is better to correct immediately after the error occurs or whether it is better to wait until immediately before the next opportunity to respond. In addition, it aimed to determine whether corrections delivered at different times produced different learner affects. Four children with autism were taught to label two sets of pictures under the two different conditions. Results showed that the timing of the feedback yields similar results in regards to number of correct responses and total trial count. However, in regards to time spent in teaching and learner affect, correcting errors before the next opportunity to respond showed to be the more efficient procedure and produced more favorable affect.
Date: December 2016
Creator: Cochrane, Angela J.
System: The UNT Digital Library
Evaluation of Agreement among Respondents to Anecdotal Assessments and Correspondence between Anecdotal and Experimental Analysis Outcomes (open access)

Evaluation of Agreement among Respondents to Anecdotal Assessments and Correspondence between Anecdotal and Experimental Analysis Outcomes

Study 1 evaluated agreement among five respondents using the Functional Analysis Screening Tool (FAST), the Motivation Assessment Scale (MAS) and Questions About Behavioral Function (QABF). Respondents provided ratings for 20 target behaviors exhibited by 10 individuals. At least 4/5 raters agreed on the primary maintaining variable in 80% of cases with the FAST, 70% of cases with the MAS, and 55% of cases with the QABF. Study 2 evaluated correspondence between results of anecdotal assessments and experimental functional analysis for 10 target behaviors selected from Study 1. Correspondence between the experimental functional analyses was 60% with the FAST and the MAS, 50% with the QABF.
Date: December 2016
Creator: Frusha, Caroline J.
System: The UNT Digital Library